Underground drilling systems often use a rotary drilling tool to form a bore in the ground. The rotary drilling tool is typically mounted at a distal end of a drill string including a plurality of drill rods (e.g., drill pipes) strung together end-to-end. The drill string transfers thrust and torque from a proximal drive mechanism (e.g., an above-ground drive mechanism) to the rotary drilling tool. In this way, the drill string is used to rotate the rotary drilling tool about a longitudinal axis of the drill string and is concurrently used apply thrust in a distal direction to the rotary drilling tool. Drill rods are progressively added to the drill string to increase the length of the bore. For certain applications, the rotary drilling tool includes structure (e.g., a slanted/angled face) that allows the rotary drilling tool to be steered to control the direction in which the bore is drilled. A sonde can be provided adjacent the rotary drilling tool for use in monitoring operational parameters of the rotary drilling tool such as pitch and rotational orientation (i.e., roll or clock position). The sonde can also work with other equipment to allow a geographic position of the drilling tool to be determined. The sonde typically interfaces with a control system that used to control the direction in which the rotary drilling tool travels. An example drilling system including a sonde is disclosed in U.S. Pat. No. 7,172,035, which is hereby incorporated by reference in its entirety.